/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.handler;

import java.util.Collections;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.Ordered;
import org.springframework.lang.Nullable;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

/**
 * A {@link HandlerExceptionResolver} that delegates to a list of other
 * {@link HandlerExceptionResolver HandlerExceptionResolvers}.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class HandlerExceptionResolverComposite implements HandlerExceptionResolver, Ordered {

    @Nullable
    private List<HandlerExceptionResolver> resolvers;

    private int order = Ordered.LOWEST_PRECEDENCE;


    /**
     * Set the list of exception resolvers to delegate to.
     */
    public void setExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        this.resolvers = exceptionResolvers;
    }

    /**
     * Return the list of exception resolvers to delegate to.
     */
    public List<HandlerExceptionResolver> getExceptionResolvers() {
        return (this.resolvers != null ? Collections.unmodifiableList(this.resolvers) : Collections.emptyList());
    }

    public void setOrder(int order) {
        this.order = order;
    }

    @Override
    public int getOrder() {
        return this.order;
    }


    /**
     * Resolve the exception by iterating over the list of configured exception resolvers.
     * <p>The first one to return a {@link ModelAndView} wins. Otherwise {@code null}
     * is returned.
     */
    @Override
    @Nullable
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response,
                                         @Nullable Object handler, Exception ex) {

        if (this.resolvers != null) {
            for (HandlerExceptionResolver handlerExceptionResolver : this.resolvers) {
                ModelAndView mav = handlerExceptionResolver.resolveException(request, response, handler, ex);
                if (mav != null) {
                    return mav;
                }
            }
        }
        return null;
    }

}
